Harriet Harman, Labour's deputy leader, said the UK government would "seek for him to be sentenced to serve prison in this country", despite McKinnon losing his latest appeal against extradition last week.

McKinnon is accused of breaking into US military computers, including those belonging to NASA, in 2001, in a bid to prove the US government had knowledge of UFOs. In 2008, the European Court of Human Rights agreed to McKinnon's extradition.

However, McKinnon challenged the ruling, first by claiming he would plead guilty to the charges if he was tried in the UK. When the British Crown Prosecution Service (CPS) refused to co-operate, McKinnon, who suffers from Asperger's Syndrome, sought a judicial review of the decision to extradite him, with his lawyers claiming his removal from the UK could possibly lead to suicide.

The judges working on the review revealed last week that McKinnon's bid had failed and that extradition was "a lawful and proportionate response to his offending".

However, Harmann told the BBC's Sunday AM programme yesterday that the British government had received assurances from the US McKinnon's health needs will be attended to if the extradition takes place.

McKinnon's plight has been a hot topic amongst leading government figures over the past few days. Home secretary Alan Johnson said it would be illegal for a government minister to prevent the extradition.

"After all he was sitting in his bedroom by his computer, as a kind of computer geek zapping the American defence system, and therefore he was committing an offence on British soil."